Voltage detecting device for assembled battery

ABSTRACT

In a voltage detecting device, a control unit turns on first switches and fifth switches corresponding to a plurality of unit batteries of an assembled battery to charge electric charge to first capacitors. The control unit simultaneously turns off at least one of the first switches or the fifth switches to hold the electric charge in the first capacitors. While selecting one of the unit batteries in a predetermined order as a target unit battery for voltage detection, the control unit temporarily turns off a fourth switch to reset electric charge of a second capacitor, and then turns of second switches and third switches in a state where one of the first switches and one of the fifth switches corresponding to the target unit battery are kept in an off state, thereby to detect a voltage of the target unit battery.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No.2012-282517 filed on Dec. 26, 2012 and No. 2013-220111 filed on Oct. 23,2013, the disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a voltage detecting device fordetecting a voltage of each of unit batteries of an assembled battery.

BACKGROUND

An assembled battery is mounted in a hybrid vehicle or an electricvehicle. The assembled battery includes a plurality of rechargeablebatteries, as unit batteries, connected in series to each other. In suchan assembled battery, it is necessary to detect a voltage of each of theunit batteries so as to protect and manage each of the unit batteries.However, in the assembled battery used for the hybrid vehicle or theelectric vehicle, the number of series connection of the unit batteriesis very large. Therefore, the potential of the unit batteries increasestoward a higher potential position. That is, the unit battery connectedat a higher potential position in the assembled battery has a potentialhigher than the unit battery connected at a lower potential position inthe assembled battery. Therefore, a higher voltage is applied to thevoltage detecting device of the unit battery.

JP 2012-118003 A, which corresponds to US 2012/0139545 A1, discloses avoltage detecting device for an assembled battery. In the voltagedetecting device of JP 2012-118003 A, an operation amplifier and aswitch are provided by a low withstand voltage transistor, without usinga high withstand voltage transistor. The voltage detecting deviceincludes a first capacitor for each of the unit batteries. A firstswitch is disposed between a first end of the first capacitor and a highpotential terminal of the unit battery, and a second switch is disposedbetween the first end of the first capacitor and a low potentialterminal of the unit battery. A third switch is disposed between asecond end of the first capacitor and an inverted input terminal of theoperation amplifier. A second capacitor and a fourth switch areconnected in parallel with each other, between an input terminal of theoperation amplifier and an output terminal of the operation amplifier.

In the voltage detecting device, one of a plurality of unit batteries isselected as a target of voltage detection in a predetermined order. Thefirst switch, the third switch and the fourth are turned on toaccumulate electric charge of the unit battery selected as the voltagedetection target in the first capacitor. Thereafter, the first switchand the fourth switch are turned off and the second switch is turned onto detect the voltage of the selected unit battery.

SUMMARY

When the unit battery deteriorates, for example, an internal resistanceincreases and a terminal open circuit voltage (electromotive force)reduces. Therefore, a management device for the assembled battery needsto simultaneously detect the voltage of each of the unit batteries and acurrent flowing in the entirety of the assembled battery so as tomeasure the internal resistance and the terminal open circuit voltage ofeach of the unit batteries at high accuracy.

In the voltage detecting device disclosed in JP 2012-118003 A, the unitbatteries are selected as the voltage detection target in a sequenceorder. The electric charge according to the voltage of the selected unitbattery is held in the first capacitor for sampling the voltage, therebydetecting the battery voltage.

When this voltage detecting device is used to measure the internalresistance and the terminal open circuit voltage, it is necessary tosample the voltage each time the unit battery is selected as the voltagedetection target. Also, it is necessary to detect the current flowing inthe assembled battery each time the voltage of the unit battery issampled. Therefore, the sampling time and the number of times ofdetecting the current increase. As a result, the time of measuring theinternal resistance and the time of measuring the terminal open circuitvoltage of the unit batteries increase.

It is an object of the present disclosure to provide an assembledbattery that detects voltages of a plurality of unit batteries whilesimultaneously sampling the plurality of unit batteries.

According to a first aspect of the present disclosure, a voltagedetecting device is configured to detect a voltage of each of aplurality of unit batteries of an assembled battery. The plurality ofunit batteries is connected in series. The voltage detecting deviceincludes an operation amplifier, a plurality of first capacitors, aplurality of first switches, a plurality of second switches, a pluralityof third switches, a second capacitor, a fourth switch, a plurality offifth switches, and a control unit. The operation amplifier has aninverted input terminal and a non-inverted input terminal. The firstcapacitors is correspondingly provided for the unit batteries. Each ofthe first switches is disposed between a high potential terminal ofcorresponding one of the unit batteries and a first end of correspondingone of the first capacitors. Each of the second switches is disposedbetween a low potential terminal of corresponding one of the unitbatteries and the first end of corresponding one of the firstcapacitors. Each of the third switches is disposed between the invertedinput terminal of the operation amplifier and a second end ofcorresponding one of the first capacitors. The second capacitor and thefourth switch are disposed in parallel between the inverted inputterminal of the operation amplifier and an output terminal of theoperation amplifier. Each of the fifth switches is disposed between avoltage line applied with a specified voltage and the second end ofcorresponding one of the first capacitors. The control unit controls thefirst switches, the second switches, the third switches, the fourthswitch and the fifth switches to detect the voltage of each of the unitbatteries. The control unit closes the first switches and the fifthswitches to charge electric charge to the plurality of first capacitors,and simultaneously opens at least one of the first switches or the fifthswitches to hold the electric charge in the first capacitors. Then,while selecting one of the unit batteries in a predetermined order as atarget unit battery for voltage detection, the control unit temporarilycloses the fourth switch to reset electric charge of the secondcapacitor, and then closes one of the second switches corresponding tothe target unit battery and one of the third switches corresponding tothe target unit battery, in a state where one of the first switchescorresponding to the target unit battery and one of the fifth switchescorresponding to the target unit battery are opened, thereby to detectthe voltage of the target unit battery.

In the above voltage detecting device, the electric charge of the unitbatteries is sampled at the same time, and then the voltages of the unitbatteries are detected in a predetermined order using the electriccharge sampled. Therefore, the time of measuring the internal resistanceand the terminal open circuit voltage of the unit batteries can beshortened, as compared with a conventional structure.

According to a second aspect of the present disclosure, a voltagedetecting device is configured to detect a voltage of each of aplurality of unit batteries of an assembled battery. The plurality ofunit batteries is connected in series. The voltage detecting deviceincludes an operation amplifier, a plurality of first capacitors, aplurality of first switches, a plurality of second switches, a pluralityof third switches, a second capacitor, a fourth switch and a controlunit. The operation amplifier has an inverted input terminal and anon-inverted input terminal. The first capacitors are correspondinglyprovided for the unit batteries. Each of the first switches is disposedbetween a high potential terminal of corresponding one of the unitbatteries and a first end of corresponding one of the first capacitors.Each of the second switches is disposed between a low potential terminalof corresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors. Each of the third switches isdisposed between the inverted input terminal of the operation amplifierand a second end of corresponding one of the first capacitors. Thesecond capacitor and the fourth switch are disposed in parallel betweenthe inverted input terminal of the operation amplifier and an outputterminal of the operation amplifier. The control unit controls the firstswitches, the second switches, the third switches, and the fourth switchto detect the voltage of each of the unit batteries. The control unitcloses the first switches and the third switches to charge electriccharge to the plurality of first capacitors, in a state where the fourthswitch is closed and the operation amplifier is operated in a voltagefollower, and then simultaneously opens at least one of the firstswitches or the third switches to hold the electric charge in the firstcapacitors. While selecting one of the unit batteries in a predeterminedorder as a target unit battery for voltage detection, the control unittemporarily closes the fourth switch to reset electric charge of thesecond capacitor, and closes one of the second switches corresponding tothe target unit battery and one of the third switches corresponding tothe target unit battery, in a state where one of the first switchescorresponding to the target unit battery is opened, thereby to detectthe voltage of the target unit battery.

The voltage detecting device according to the second aspect has asimilar structure to the voltage detecting device according to the firstaspect, but does not include the fifth switches. Also in this case, thesimilar advantageous effects will be achieved.

According to a third aspect of the present disclosure, a voltagedetecting device is configured to detect a voltage of each of aplurality of unit batteries of an assembled battery. The plurality ofunit batteries is connected in series. The voltage detecting deviceincludes an operation amplifier, a plurality of first capacitors, aplurality of first switches, a plurality of second switches, a pluralityof third switches, a fourth switch, a second capacitor, a ninth switch,a tenth switch and a control unit. The operation amplifier has aninverted input terminal and a non-inverted input terminal. The firstcapacitors are correspondingly provided for the unit batteries. Each ofthe first switches is disposed between a high potential terminal ofcorresponding one of the unit batteries and a first end of correspondingone of the first capacitors. Each of the second switches is disposedbetween a low potential terminal of corresponding one of the unitbatteries and the first end of corresponding one of the firstcapacitors. Each of the third switches is disposed between the invertedinput terminal of the operation amplifier and a second end ofcorresponding one of the first capacitors. The fourth switch is disposedbetween the inverted input terminal of the operation amplifier and anoutput terminal of the operation amplifier. The second capacitor and theninth switch are disposed in series, between the inverted input terminalof the operation amplifier and the output terminal of the operationamplifier. The tenth switch is disposed between a common connectingpoint of the second capacitor and the ninth switch and a voltage lineapplied with a constant voltage. The control unit controls the firstswitches, the second switches, the third switches, the fourth switch,the ninth switch and the tenth switch to detect the voltage of each ofthe unit batteries. The control unit closes the first switches and thethird switches to charge electric charge to the plurality of firstcapacitors, in a state where the fourth switch is closed and theoperation amplifier is operated in a voltage follower, and thensimultaneously opens at least one of the first switches or the thirdswitches to hold the electric charge in the first capacitors. Whileselecting one of the unit batteries in a predetermined order as a targetunit battery for voltage detection, the control unit temporarily closesthe fourth switch and the tenth switch to reset electric charge of thesecond capacitor, and closes the ninth switch, one of the secondswitches corresponding to the target unit battery, and one of the thirdswitches corresponding to the target unit battery, in a state where oneof the first switches corresponding to the target unit battery isopened, thereby to detect the voltage of the target unit battery.

In the voltage detecting device according to the third aspect, theadvantageous effects similar to the voltage detecting device accordingto the second aspect will be achieved. Further, an offset voltage of theoperation amplifier can be removed from the detected voltage of the unitbattery.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings, in whichlike parts are designated by like reference numbers and in which:

FIG. 1 is a schematic diagram of a voltage detecting device according toa first embodiment of the present disclosure;

FIG. 2 is a schematic diagram of a part of the voltage detecting device,including a first switch, a second switch and a drive circuit of thefirst and second switches, according to the first embodiment;

FIG. 3 is a schematic diagram of a level shift circuit of the voltagedetecting device according to the first embodiment;

FIG. 4 is a schematic diagram of a non-overlap signal generation circuitof the voltage detecting device according to the first embodiment;

FIG. 5 is a time chart of the non-overlap signal generation circuitaccording to the first embodiment;

FIG. 6 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the first embodiment;

FIG. 7 is a schematic diagram of a voltage detecting device according toa second embodiment of the present disclosure;

FIG. 8 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the second embodiment;

FIG. 9 is a schematic diagram of a voltage detecting device according toa third embodiment of the present disclosure;

FIG. 10 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the second embodiment;

FIG. 11 is a schematic diagram of a voltage detecting device accordingto a fourth embodiment of the present disclosure;

FIG. 12 is a schematic diagram of a voltage detecting device accordingto a fifth embodiment of the present disclosure;

FIG. 13 is a schematic diagram of a voltage detecting device accordingto a sixth embodiment of the present disclosure;

FIG. 14 is a schematic diagram of a voltage detecting device accordingto a seventh embodiment of the present disclosure;

FIG. 15 is a schematic diagram of a voltage detecting device accordingto an eighth embodiment of the present disclosure;

FIG. 16 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the eighth embodiment;

FIG. 17 is a schematic diagram of a voltage detecting device accordingto a ninth embodiment of the present disclosure;

FIG. 18 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the ninth embodiment;

FIG. 19 is a schematic diagram of a voltage detecting device accordingto a tenth embodiment of the present disclosure;

FIG. 20 is a diagram illustrating on and off states of switches, awaveform of an output voltage, and voltage detection states of cellbatteries according to the tenth embodiment;

FIG. 21 is a schematic diagram of a voltage detecting device accordingto an eleventh embodiment of the present disclosure;

FIG. 22 is a schematic diagram of a voltage detecting device accordingto a twelfth embodiment of the present disclosure;

FIG. 23 is a schematic diagram of a voltage detecting device accordingto a thirteenth embodiment of the present disclosure;

FIG. 24 is a schematic diagram of a voltage detecting device accordingto a fourteenth embodiment of the present disclosure;

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the present disclosure will bescavenger described with reference to the drawings. Like parts will bedesignated with like reference numbers, and descriptions thereof willnot be repeated.

First Embodiment

A first embodiment will be described with reference to FIGS. 1 to 6.

Referring to FIG. 1, an assembled battery 1 is, for example, mounted ina hybrid vehicle or an electric vehicle. The assembled battery 1supplies electric power to an electric motor through an inverter.

The assembled battery 1 includes a plurality of unit batteries connectedin series. In an actual assembled battery 1, a large number of lithiumrechargeable batteries, a large number of nickel hydride rechargeablebatteries, or the like are connected in series, as the unit batteries.In FIG. 1, four battery cells, such as a battery cell B1 on alow-potential side to a battery cell B4 on a high-potential side, areexemplarily illustrated for the convenience of explanation. The batterycell corresponds to the unit battery.

When the battery cell deteriorates, an increase in internal resistance,a decrease in terminal open circuit voltage (electromotive force), andthe like occur. A management device (not shown) for the assembledbattery 1 measures the internal resistance and the terminal open circuitvoltage of each of the battery cells B1 to B4 by simultaneouslydetecting the voltage of each of the battery cells B1 to B4 and thecurrent flowing in the entirety of the assembled battery 1 using avoltage detecting device 2 shown in FIG. 1 and a current detectingdevice (not shown). In order to measure the internal resistance and theterminal open circuit voltage at high accuracy, it is necessary tosample the voltage and the current simultaneously.

Terminals of the battery cells B1 to B4 are connected to terminals TB0to TB4 of the voltage detecting device 2, respectively. The voltages ofthe terminals TB0 to TB4 are denoted as V0 to V4, respectively. Thevoltage detecting device 2 samples the battery cells Bn (n=1, 2, 3, 4)at the same time. Thereafter, the voltage detecting device 2 detects thecell voltage VBn of the battery cell Bn using the electric charge heldin a sequence order, and outputs the detected cell voltage VBn in asequence order as an output voltage VOUT from an output terminal TP toan analog-to-digital (A/D) converter 3.

The voltage detecting device 2 may be configured as an integratedcircuit (IC) together with other circuits, such as the A/D converter 3.The voltage detecting device 2 includes an operation amplifier 4 havinga single end output structure. In other words, the operation amplifier 4is a single end operation amplifier. The operation amplifier 4 isconfigured to operate with application of a power supply voltage VDDspecified relative to a ground electric potential VSS. A non-invertedinput terminal of the operation amplifier 4 is biased to a referencevoltage VREF by a voltage generation circuit 5. A second capacitor C2and a fourth switch SW4 are connected in parallel, between an invertedinput terminal of the operation amplifier 4 and an output terminal ofthe operation amplifier 4.

Capacitance switching circuits having the same structure are providedbetween the terminals TBn and the operation amplifier 4 correspondinglyto the battery cells Bn. For example, the capacitance switching circuitcorresponding to the battery cell B4 includes a first capacitor C1D, afirst switch SW1D, a second switch SW2D, a third switch SW3D, and afifth switch SW5D. The first switch SW1D is connected between ahigh-potential terminal TB4 of the battery cell B4 and a first end ofthe first capacitor C1D. The second switch SW2D is connected between alow-potential terminal TB3 of the battery cell B4 and the first end ofthe first capacitor C1D. The low-potential terminal TB3 has a potentiallower than the high-potential terminal TB4. The third switch SW3D isconnected between a second end of the first capacitor C1D and a commonline CL connecting to the inverted input terminal of the operationamplifier 4. The second end of the first capacitor C1D can be appliedwith a specified voltage VREF, which is set equal to the referencevoltage, through the fifth switch SW5D.

The other capacitance switching circuits for the other battery cells Bnare configured similar to the capacitance switching circuit for thebattery cell B4. Namely, the capacitance switching circuit for onebattery cell Bn includes the first capacitor C1 x, the first switch SW1x, the second switch SW2 x, the third switch SW3 x, and the fifth switchSW5 x. The suffix “x” is any of “A”, “B”, “C” and “D” in a potentialincreasing order, that is, in an order from the low-potential sidetoward the high-potential side. Also, “A”, “B”, “C” and “D” correspondto “1”, “2”, “3”, and “4” of the above-noted “n”, respectively. Each ofthe switches is provided by a metal oxide semiconductor (MOS)transistor. The switches are controlled by a control circuit 6. Thecontrol circuit 6 corresponds to a control unit.

FIG. 2 shows a structure of the first switch SW1D and the second switchSW2D, which are disposed adjacent to the assembled battery 1 from thefirst capacitor C1 x, and a drive circuit for the first switch SW1D andthe second switch SW2D. The drive circuit for the first switch SW1D andthe second switch SW2D includes a level shift circuit 7 (LVL SFT) and anon-overlap signal generation circuit 12 (N-OLP SG GN). The level shiftcircuit 7 functions to insulate and to shift the level of a signal S1that has the ground potential VSS outputted from the control circuit 6as a reference potential.

As shown in FIG. 3, the level shift circuit 7 includes inverters 8, 9,10 and a capacitor 11. The inverter 8 is operated with application ofthe power supply voltage VDD relative to the ground potential as areference potential, similar to the control circuit 6. The inverters 9,10 are operated with application of a voltage VB4 (=V4−V3) relative to apotential V3 of the terminal TB3 as a reference potential. The capacitor11 insulates between the reference potential circuits. The inverters 9,10 are connected in a ring shape. The capacitor 11 is connected betweenan output terminal of the inverter 8 and an input terminal of theinverter 10.

When the signal S1 is inputted to the inverter 8 and the level of thesignal S1 is changed, an input electric potential of the inverter 10 ischanged through the capacitor 11. Therefore, the input level of theinverter 10 exceeds a threshold value, and an output signal S2 of theinverter 10 is inverted. The signal S2 is inverted through the inverter9 and applied to the input terminal of the inverter 10. Thus, the signalS2 is outputted in a stable manner. A drive circuit with the groundelectric potential VSS as a reference potential can be used for thethird switch SW3 x, the fourth switch SW4 x and the fifth switch SW5 x,and therefore, the level shift circuit 7 is unnecessary.

As shown in FIG. 2, the first switch SW1D is, for example, provided by alow withstand voltage PMOS transistor. The second switch SW2D is, forexample, provided by a low withstand voltage NMOS transistor. Thenon-overlap signal generation circuit 12 receives the signal S2described above, and generates and outputs drive signals S3, S4 to thefirst switch SW1D and the second switch SW2D so as to activate only oneof the first switch SW1D and the second switch SW2D according to thelevel of the signal S2.

As shown in FIG. 4, the non-overlap signal generation circuit 12includes a series circuit of an NAND gate 13 and inverters 14 to 17 anda series circuit of an NAND gate 19 and inverters 20 to 23. Theinverters 14 to 17 and the inverters 20 to 23 are provided to generate atime delay. An output terminal of the inverter 17 is connected to aninput terminal of the NAND gate 19. An output terminal of the inverter23 is connected to an input terminal of the NAND gate 13.

As shown in FIG. 5, in the non-overlap signal generation circuit 12,when the signal S2 inputted to the NAND gate 13 and the inverter 18 isat a low level (L-level, voltage V3), the drive signals S3, S4 are at ahigh level (H-level, voltage V4). When the signal S2 is at a high level(H-level), the drive signals S3, S4 are at a low level (L-level). Whenthe level of the signal S2 changes, a non-overlapping period where thedrive signal S3 is at the high level and the drive signal S4 is at thelow level occurs. Thus, it is less likely that the first switch SW1D andthe second switch SW2D will be on simultaneously.

Next, operation and advantageous effects of the present embodiment willbe described with reference to FIG. 6.

The control circuit 6 controls the switches SW1A to SW1D, SW2A to SW2Dso that the first capacitors C1A to C1D simultaneously hold the electriccharge according to the voltages VB1 to VB4 of corresponding batterycells B1 to B4. Thereafter, the control circuit 6 switches the SW1A toSW1D, SW2A to SW2D to select the battery cell from the battery cells B1to B4 as a voltage detection target in an descending order, and toperform redistribution of the electric charge held, thereby to detectthe cell voltage VB1 to VB4. The A/V converter 3 performs ananalog-to-digital conversion of the detected voltage that is outputtedfrom the voltage detection device 2 in a sequence order. In regard tothe status of the switches in FIG. 6, a high level indicates an on state(e.g., closed state) of the switch, and a low level indicates an offstate (e.g., opened state) of the switch.

[Period 1]

The control circuit 6 turns on the first switches SW1A to SW1D, thefourth switch SW4, and the fifth switches SW5A to SW5D, and turns offthe second switches SW2A to SW2D and the third switches SW3A to SW3D,for all of the battery cells B1 to B4. Thus, the first capacitors C1A toC1D are charged all together at the voltage Vn-VREF (sampling). Thesecond capacitor C2 is reset such that the electric charge of the secondcapacitor C2 is zero.

In this case, the second switches SW2A to SW2D, which are in the offstate, are applied with only the voltages VB1 to VB4, respectively. Theinput terminal of the operation amplifier 4 is applied with thereference voltage VREF, which is lower than the power supply voltageVDD. Since the reference voltage VREF and the specified voltage VREF areequal, the third switches SW3A to SW3D are applied with no voltage.

[Period 2]

The control circuit 6 turns off the fifth switches SW5A to SW5Dsimultaneously (at the same time) to hold the electric charge of thebattery cells B1 to B4 in the first capacitors C1A to C1D at the sametime. In this case, the control circuit 6 may turn off the firstswitches SW1A to SW1D at the same time or turn off the first switchesSW1A to SW1D and the fifth switches SW5A to SW5D at the same time aslong as the electric charge can be held. In other words, the controlcircuit 6 simultaneously turns off at least one of the first switchesSW1A to SW or the fifth switches SW5A to SW5D.

The current detecting device, which is not shown, detects the electriccurrent flowing in the assembled battery 1 at the same time the controlcircuit 6 turns off at least one of the first switches SW1A to SW1D orthe fifth switches SW5A to SW5D. The period 1 and the period 2 are notonly the charging period and the holding period, but also a resettingperiod of the second capacitor C2, when the battery cell B4 is thevoltage detection target.

[Period 3]

The control circuit 6 selects the battery cell B4 as the voltagedetection target. The control circuit 6 turns off the first switch SW1Dcorresponding to the battery cell B4 and the fourth switch SW4 inpreparation for the electric charge redistribution of a period 4. Thefirst switches SW1A to SW1C may be kept in the on state.

[Period 4]

The control circuit 4 turns on the second switch SW2D and the thirdswitch SW3D for the battery cell B4. Thus, the first end of the firstcapacitor C1D is applied with the voltage V3, in place of the voltageV4. In this case, the electric charge held in the first capacitor C1D inthe period 2 is redistributed with the second capacitor C2. Conservationof the electric charge between the period 3 and the period 4 isexpressed by a general formula (1), in which C1 denotes a capacitance ofthe first capacitor and C2 denotes a capacitance of the secondcapacitor. In regard to the battery cell B4, Vn=V4, and Vn−1=V3.

C1(Vn−VREF)=C1(Vn−1−VREF)+C2(VOUT−VREF)  (1)

The following formula (2) is derived from the formula (1).

VOUT=C1/C2(Vn−Vn−1)+VREF  (2)

That is, after the redistribution of the electric charge, the outputvoltage VOUT of the operation amplifier 4 becomes the voltage calculatedby multiplying the terminal voltage of the battery cell B4 (i.e., thevoltage VB4 of the battery cell B4) by C1/C2 and offsetting by thereference voltage VREF. Even in this case, the first switch SW1D and thesecond switches SW2A to SW2C, which are in the off state, are appliedonly with the voltages VB1 to VB4 of the battery cells B1 to B4,respectively.

[Period 5]

The control circuit 6 switches the voltage detection target (i.e.,target cell) from the battery cell B4 to the battery cell B3. For thebattery cell B4, which is not the target cell, the third switch SW3D isturned off to separate the first capacitor C1D from the common line CL.Further, the second switch SW2D is turned off, and the first switch SW1Dand the fifth switch SW5D are turned on to perform a sampling operation.

By the operation of the non-overlap signal generation circuit 12, thefirst switch SW1D and the second switch SW2D are not turned on at thesame time. In the period 5, the control circuit 6 temporarily turns onthe fourth switch SW4 so as to reset the electric charge of the secondcapacitor C2.

[Period 6]

Similar the period 3, the control circuit 6 turns off the first switchSW1C and the fourth switch SW4 in preparation for the electric chargeredistribution of a period 7. The first switches SW1A, SW1B, SW1D may bekept in the on state.

[Period 7]

Similar to the period 4, the control circuit 6 turns on the secondswitch SW2C and the third switch SW3C for the battery cell B3. In thiscase, the electric charge held in the first capacitor C1C in the period2 is redistributed with the second capacitor C2. The output voltage VOUTof the operation amplifier 4 is expressed by the formula (2) (in thiscase, Vn=V3, Vn−1=V2).

[Period 8 to period 13]

In periods 8 to 10, the control circuit 6 selects the battery cell B2 asthe target cell, and obtains the output voltage VOUT expressed by theformula (2) (Vn=V2, Vn−1=V1), similar to the periods 5 to 7.Subsequently, in periods 11 to 13, the control circuit 6 selects thebattery cell B1 as the target cell, and obtains the output voltage VOUTexpressed by the formula (2) (Vn=V1, Vn−t=V0), similar to the periods 5to 7.

In this way, one cycle of detection of the cell voltages VB1 to VB4 isperformed through the periods 1 to 13. The voltage detecting device 2repeatedly performs the process from the period 1 to the period 13 inaccordance with the command from the management device.

In the present embodiment, as described above, the voltage detectingdevice 2 samples the battery cells Bn at the same time, and then detectsthe cell voltages VBn using the sampled electric charge in a sequenceorder. The capacitance switching circuit including the first capacitorC1 x and the switches is provided for each of the battery cells Bn.Therefore, a layout area is reduced, as compared with a structure inwhich a specific A/D converter is provided for each of the battery cellsBn and the sampling is performed at the same time for the battery cellsBn.

The management device for the assembled battery 1 performs sampling ofthe electric current at the same time as sampling the electric charge.Therefore, for the plurality of battery cells Bn, the internalresistance and the terminal open circuit voltage (electromotive force)of each of the battery cells Bn can be accurately measured by samplingthe electric current one time.

In this measuring method, the measuring time can be shortened, ascompared with a conventional structure. Further, the calculation fordetecting the electric current is performed one time for the pluralityof battery cells Bn. Therefore, the amount of calculation for detectingthe electric current reduces. As such, the management device may beprovided by using less expensive microcomputer with a low calculationcapacity.

The first switches SW1 x and the second switches SW2 x, which forms acircuit adjacent to the assembled battery 1, are only applied with avoltage equal to or lower than the voltage VBn of the single batterycell. The level shift circuit 7 provided with the capacitor 11 forinsulation and separation is used to drive the first switch SW1 x andthe second switch SW2 x. Since the reference voltage and the specificvoltage are set equal to each other, the third switch SW3 x and thefifth switch SW5 x, which form a circuit adjacent to the operationamplifier 4, are applied with no voltage. Further, the fourth switch SW4is only applied with a voltage equal to or lower than the power supplyvoltage VDD. According to these structures, the operation amplifier 4and all of the switches can be provided by low withstand voltagetransistors. Moreover, since there is no electric charge omission fromthe first capacitor C1 x in accordance with the drive of the switch, thecell voltage VBn can be detected at high accuracy.

The first capacitor C1 x needs to withstand a high voltage over thepower supply voltage VDD. When an interlayer insulation film of a metalwiring is used, the high voltage withstand can be ensured. Therefore, aspecific manufacturing step is unnecessary. As such, the voltagedetecting device 2 can be constructed as the IC using the low withstandvoltage transistors, such as 5V-system or 3.3 V-system. With this, sincethe layout area reduces, the manufacturing costs reduce.

Second Embodiment

A second embodiment will be described with reference to FIGS. 7 and 8.

As shown in FIG. 7, a voltage detecting device 31 has a similarstructure to the voltage detecting device 2 shown in FIG. 1, but doesnot have the fifth switches SW5A to SW5D. The control circuit 6simultaneously samples the battery cells B1 to B4, and controls theswitches to simultaneously hold the electric charge in the firstcapacitors C1A to C1D. Thereafter, the control circuit 6 controls theswitches to select one of the battery cells B1 to B4 in a descendingorder as the target cell. The control circuit 6 performs theredistribution of the electric charge held, thereby to detect thevoltage of each of the battery cells VB1 to VB4.

[Period 1]

The control circuit 6 turns on the first switches SW1A to SW1D, thethird switches SW3A to SW3D and the fourth switch SW4, and turns off thesecond switches SW2A to SW2D, for all of the battery cells B1 to B4.Thus, the operation amplifier 4 is operated as a voltage follower, andthe first capacitors C1A to C1D are simultaneously charged at thevoltage Vn−VREF (sampling). The electric charge of the second capacitorC2 is reset to zero. In this case, the second switches SW2A to SW2D,which are in the off state, are only applied with the voltages VB1 toVB4 of the battery cells B1 to B4, respectively.

[Period 2]

The control circuit 6 turns off the third switches SW3A to SW3Dsimultaneously (at the same time) to hold the electric charge of thebattery cells B1 to B4 in the first capacitors C1A to C1D at the sametime (holding). The control circuit 6 may simultaneously turn off thefirst switches SW1A to SW1D, or may simultaneously turn off the firstswitches SW1A to SW1D and the third switches SW3A to SW3D, as long asthe electric charge can be held. That is, the control circuit 6 maysimultaneously turn off at least one of the first switches SW1A to SW1Dor the third switches SW3A to SW3D.

The current detecting device (not shown) detects the electric currentflowing in the assembled battery 1 at the same time as the holding. Theperiod 1 and the period 2 are not only the charging period and theholding period, but also a resetting period of the second capacitor C2,when the battery cell B4 is the voltage detection target (i.e., targetcell).

[Period 3]

The control circuit 6 selects the battery cell B4 as the target cell.The control circuit 6 turns off the first switch SW1D and the fourthswitch SW4 in preparation for the electric charge redistribution of aperiod 4. The first switches SW1A to SW1C may be kept in the on state,and the third switches SW3A to SW3C may be kept in the off state.

[Period 4]

The control circuit 4 turns on the second switch SW2D and the thirdswitch SW3D for the battery cell B4. Thus, the first end of the firstcapacitor C1D is applied with the voltage V3, in place of the voltageV4. In this case, the electric charge held in the first capacitor C1D inthe period 2 is redistributed with the second capacitor C2. Theconservation of the electric charge between the period 3 and the period4 is expressed by the formula (1), and the output voltage VOUT of theoperation amplifier 4 is expressed by the formula (2). In regard to thebattery cell B4, Vn=V4, and Vn−1=V3.

[Period 5]

The control circuit 6 switches the target cell from the battery cell B4to the battery cell B3. For the battery cell B4, which is not the targetcell, the second switch SW2D and the third switch SW3D are turned off toshift to a standby operation. Since the control circuit 6 resets theelectric charge of the second capacitor C2, the fourth switch SW4 istemporarily turned on in this period.

[Period 6]

Similar the period 3, the control circuit 6 turns off the first switchSW1C and the fourth switch SW4 in preparation for the electric chargeredistribution of a period 7. The first switches SW1A and SW1D may bekept in the on state.

[Period 7]

Similar to the period 4, the control circuit 6 turns on the secondswitch SW2C and the third switch SW3C for the battery cell B3. In thiscase, the electric charge held in the first capacitor C1C in the period2 is redistributed with the second capacitor C2. The output voltage VOUTof the operation amplifier 4 is expressed by the formula (2) (in thiscase, Vn=V3, and Vn−1=V2).

[Period 8 to period 13]

In periods 8 to 10, the control circuit 6 selects the battery cell B2 asthe target cell, and obtains the output voltage VOUT expressed by theformula (2) (Vn=V2, Vn−1=V1), similar to the periods 5 to 7.Subsequently, in periods 11 to 13, the control circuit 6 selects thebattery cell B1 as the target cell, and obtains the output voltage VOUTexpressed by the formula (2) (in this case, Vn=V1, Vn−1=V0), similar tothe periods 5 to 7.

In this way, one cycle of detection of the voltages VB1 to VB4 isperformed through the periods 1 to 13. When the process proceeds fromthe period 13 to the period 1, the control circuit 6 turns on the firstswitches SW1A to SW1D, the third switches SW3A to SW3D and the fourthswitch SW4 to simultaneously charge the first capacitors C1A to C1D. Thevoltage detecting device 31 repeatedly performs the process from theperiod 1 to the period 13 in accordance with the command from themanagement device.

In the present embodiment, the voltage detecting device 31 does not havethe fifth switches SW5A to SW5D. Therefore, the layout area can bereduced by the deletion of the fifth switches SW5A to SW5D. Also in thepresent embodiment, the advantageous effects similar to the firstembodiment will be achieved.

Third Embodiment

A third embodiment will be described with reference to FIGS. 9 and 10.

As shown in FIG. 9, a voltage detecting device 41 has a structuresimilar to the voltage detecting device 31 shown in FIG. 7, but thestructures of the second capacitor C2 and the fourth switch SW4 aremodified from those of the voltage detecting device 31 shown in FIG. 7so as to reduce the effect of an offset voltage of the operationamplifier 4.

In this case, a fourth switch SW4A is connected between the invertedinput terminal of the operation amplifier 4 and the output terminal ofthe operation amplifier 4. Further, a series circuit of the secondcapacitor C2 and a fourth switch SW4B is connected in parallel with thefourth switch SW4A. Further, a fourth switch SW4C is connected between acommon connecting point between the second capacitor C2 and the fourthswitch SW4B and the voltage line to which a constant voltage VA isapplied. The fourth switch SW4A will be also referred to as the fourth-Aswitch SW4A, the fourth switch SW4B will be also referred to as thefourth-B switch SW4B or the ninth switch SW4B, and the fourth switchSW4C will be also referred to as the fourth-C switch SW4C or the tenthswitch SW4C. The control circuit 6 controls the fourth-A switch SW4A andthe fourth-C switch SW4C so that the fourth-A switch SW4A and thefourth-C switch SW4C are always in the same state.

Structures of the voltage detecting device 41 other than the above aresimilar to those of the voltage detecting device 31.

The operation of the voltage detecting device 41 will be described withreference to FIG. 10. Hereinafter, referring to the detection of thevoltage VB4 of the battery cell B4 as an example, the operationdifferent from the first embodiment will be mainly described.

In the period 1, the control circuit 6 turns on the fourth-A switch SW4Aand the fourth-C switch SW4C, and turns off the fourth-B switch SW4B.Thus, the second capacitor C2 is reset with the electric chargeaccording to the voltage VA-VREF.

In the period 3, the control circuit 6 turns off the fourth-A switchSW4A and the fourth-C switch SW4C. In the period 4, the control circuitturns on the fourth-B switch SW4B. In the period 4, the electric chargeheld in the first capacitor C1D in the period 2 is redistributed withthe second capacitor C2. The conservation of the electric charge betweenthe period 3 and the period 4 is expressed by the following generalformula (3). The following formula (4) is derived from the formula (3).

C1(Vn−VREF)+C2(VA−VREF)=C1(Vn−1−VREF)+C2(VOUT−VREF)  (3)

VOUT=C1/C2(Vn−Vn−1)+VA  (4)

In general, the operation amplifier has an offset voltage. Consideringthe offset voltage ΔVOS of the operation amplifier 4, the conservationof the electric charge is expressed by the following general formula(5). When the formula (5) is solved, the offset voltage ΔVOS is offset,and the same result as the formula (4) is obtained.

C1(Vn−VREF+ΔVOS)+C2(VA−VREF+ΔVOS)=C1(Vn−1−VREF+ΔVOS)+C2(VOUT−VREF+ΔVOS)  (5)

In the present embodiment, since the effect of the offset voltage ΔVOSof the operation amplifier 4 can be removed from the detection voltageVBn of the cell voltage VBn, the voltage detection can be performed athigher accuracy. Also in the present embodiment, the advantageouseffects similar to the second embodiment will be achieved.

Fourth Embodiment

A fourth embodiment will be described with reference to FIG. 11.

As shown in FIG. 11, a voltage detecting device 51 includes adifferential output operation amplifier 52. That is, the voltagedetecting device 51 is provided by modifying the voltage detectingdevice 2 of the first embodiment into a full differential type. A commonvoltage VCOM of the operation amplifier 52 is set equal to the referencevoltage VREF. The operation amplifier 52 outputs a differential voltageVOP from a non-inverted output terminal and a differential voltage VOMfrom an inverted output terminal. The differential voltages VOP, VOMoutputted from output terminals TP, TM are converted into digital databy a differential input-type ND converter 53.

Symmetric circuits are provided on one side (e.g., first side) of theoperation amplifier 52 including the inverted input terminal and thenon-inverted output terminal, and the other side (e.g., second side) ofthe operation amplifier 52 including the non-inverted input terminal andthe inverted output terminal. In other words, a first-side circuit unitand a second-side circuit unit are provided with respect to theoperation amplifier 52. Each of the symmetric circuits, that is, each ofthe first-side circuit unit and the second-side circuit unit, has aconnection structure similar to the voltage detecting device 2. Inparticular, each circuit unit includes the first capacitors C1 x, thesecond capacitor C2, the first switches SW1 x, the second switches SW2x, the third switches SW3 x, the fifth switches SW5 x and the fourthswitch SW4. The suffix x is A, B, C, or D in a potential increasingorder of the capacitance switching circuits.

In the first-side circuit unit, which corresponds to the inverted inputterminal and the non-inverted output terminal of the operation amplifier52, the first switch SW1 x is disposed between the high-potentialterminal of the battery cell Bn corresponding to the first capacitor C1x and the first end of the first capacitor C1 x. The second switch SW2 xis disposed between the low-potential terminal of the battery cell Bncorresponding to the first capacitor C1 x and the first end of the firstcapacitor C1 x.

In the second-side circuit unit, which corresponds to the non-invertedinput terminal and the inverted output terminal of the operationamplifier 52, the first switch SW1 x is disposed between thelow-potential terminal of the battery cell Bn corresponding to the firstcapacitor C1 x and the first end of the first capacitor C1 x. The secondswitch SW2 x is disposed between the high-potential side terminal of thebattery cell Bn corresponding to the first capacitor C1 x and the firstend of the first capacitor C1 x.

The control circuit 6 performs a switch control similar to the firstembodiment shown in FIG. 6. In this case, the conservation of theelectric charge between the period 3 and the period 4 is expressed bythe following general formulas (6) and (7). The formula (8) is obtainedby subtracting the formula (7) from the formula (6). In the formulas (6)and (7), VX denotes a common voltage on an input side.

C1(Vn−VREF)=C1(Vn−1−VX)+C2(VOP−VX)  (6)

C1(Vn−1−VREF)=C1(Vn−VX)+C2(VOM−VX)  (7)

VOP−VOM=2C1/C2(Vn−Vn−1)  (8)

When common mode noise ΔV is overlapped on the assembled battery 1 atthe time of the electric charge redistribution of the period 4, theconservation of the electric charge is expressed by the followinggeneral formulas (9) and (10). When the formula (10) is subtracted fromthe formula (9), the item of ΔV is cancelled, and thus the same resultas the formula (8) is obtained. That is, since the voltage detectingdevice 51 is the full differential type, even if the common mode noiseΔV overlaps on the assembled battery 1 in the redistribution of theelectric charge, a differential output voltage VOP−VOM is not affected.

C1(Vn−VREF)=C1(Vn−1+ΔV−VX)+C2(VOP−VX)  (9)

C1(Vn−1−VREF)=C1(Vn+ΔV−VX)+C2(VOM−VX)  (10)

As described above, in the present embodiment, since the voltagedetecting device 51 is the full differential type, the common mode noisecan be removed from the differential output voltage VOP−VOM, not onlywhen the common mode noise is overlapped on the assembled battery 1 inthe charging of the first capacitor C1 x, but also when the common modenoise is overlapped on the assembled battery 1 in the redistribution ofthe electric charge. Moreover, since the circuit structure is symmetricwith respect to the operation amplifier 52, an error due to a fieldthrough occurring in the operations of the switches can be cancelled.Thus, the voltage can be detected at further higher accuracy. Also inthe present embodiment, the advantageous effects similar to the firstembodiment will be achieved.

Fifth Embodiment

A fifth embodiment will be described with reference to FIG. 12.

As shown in FIG. 12, a voltage detecting device 61 includes thedifferential output operation amplifier 52. That is, the voltagedetecting device 61 is provided by modifying the voltage detectingdevice 31 of the second embodiment into a full differential type.

Symmetric circuits are provided on one side (e.g., first side) of theoperation amplifier 52 including the inverted input terminal and thenon-inverted output terminal, and the other side (e.g., second side) ofthe operation amplifier 52 including the non-inverted input terminal andthe inverted output terminal. In other words, a first-side circuit unitand a second-side circuit unit are provided with respect to theoperation amplifier 52. Each of the symmetric circuits, that is, each ofthe first-side circuit unit and the second-side circuit unit, has aconnection structure similar to the voltage detecting device 31. Each ofthe first-side circuit unit and the second-side circuit unit includesthe first capacitor C1 x, the second capacitor C2, the first switchesSW1 x, the second switches SW2 x, the third switches SW3 x, and thefourth switch SW4. In other words, the voltage detecting device 61 has asimilar structure of the voltage detecting device 51 shown in FIG. 11,but the fifth switches SW5A to SW5D are deleted.

The control unit 6 performs a switch control similar to that of thesecond embodiment shown in FIG. 8. In this case, the conservation of theelectric charge between the period 3 and the period 4 is expressed bythe following general formulas (11) and (12). When the formula (12) issubtracted from the formula (11), the formula (8), which is describedhereinabove, is obtained. In the formula (11) and the formula (12), VCOMdenotes a common voltage on an output side of the operation amplifier52, and VX denotes a common voltage on an input side of the operationamplifier 52.

C1(Vn−VCOM)=C1(Vn−1−VX)C2(VOP−VX)  (11)

C1(Vn−1−VCOM)=C1(Vn−VX)+C2(VOM−VX)  (12)

In the present embodiment, the advantageous effects similar to thefourth embodiment, which is specific to the full differential structure,will be achieved. In addition, the advantageous effects similar to thesecond embodiment will also be achieved.

Sixth Embodiment

A sixth embodiment will be described with reference to FIG. 13.

A voltage detecting device 71 is provided by modifying the voltagedetecting device 41 of the third embodiment into a full differentialtype.

The first-side circuit unit, which corresponds to the inverted inputterminal and the non-inverted output terminal of the operation amplifier52 and the second-side circuit unit, which corresponds to thenon-inverted input terminal and the inverted output terminal of theoperation amplifier 52, have a connection structure similar to thevoltage detecting device 41, and include the fourth-A switch SW4A, thefourth-B switch SW4B, and the fourth-C switch SW4C. Other structures ofthe voltage detecting device 71 are similar to the structures of thevoltage detecting device 61 shown in FIG. 12.

The control unit 6 performs a switch control similar to the thirdembodiment shown in FIG. 10. The conservation of the electric chargebetween the period 3 and the period 4 is expressed by the followinggeneral formulas (13) and (14). The following formula (15) is obtainedby subtracting the formula (14) from the formula (13).

C1(Vn−VCOM)+C2(VA−VCOM)=C1(Vn−1−VX)+C2(VOP−VX)  (13)

C1(Vn−1−VCOM)+C2(VB−VCOM)=C1(Vn−VX)+C2(VOM−VX)  (14)

VOP−VOM=2C1/C2(Vn−Vn−1)+(VA−VB)  (15)

When the common mode noise ΔV is overlapped on the assembled battery 1at the time of the redistribution of the electric charge in period 4,the conservation of the electric charge is expressed by the followinggeneral formulas (16) and (17). When the formula (17) is subtracted fromthe formula (16), the item of ΔV is cancelled, and thus the same resultas the formula (15) is obtained. That is, since the voltage detectingdevice 71 is the full differential type, even if the common mode noiseΔV is overlapped on the assembled battery 1 at the time of theredistribution of the electric charge, the differential output voltageVOP−VOM is not affected.

C1(Vn−VCOM)+C2(VA−VCOM)=C1(Vn−1+ΔV−VX)+C2(VOP−VX)  (16)

C1(Vn−1−VCOM)+C2(VB−VCOM)=C1(Vn+ΔV−VX)+C2(VOM−VX)  (17)

Further, when the offset voltage VOS of the operation amplifier 52 isconsidered, the conservation of the electric charge is expressed by thefollowing formula (18), in place of the above-described formula (13).When the formula (14) is subtracted from the formula (18), the item ofLVOS is cancelled, and thus the same result as the above-describedformula (15) is obtained. That is, in the voltage detecting device 71,the effect of the offset voltage ΔVOS of the operation amplifier 52 canbe removed, similar to the third embodiment.

C1(Vn−VCOM+VOS)+C2(VA−VCOM+VOS)=C1(Vn−1−VX+VOS)+C2(VOP−VX+VOS)  (18)

In the present embodiment, the advantageous effects similar to thefourth embodiment, which is specific to the full differential structure,will be achieved. In addition, the advantageous effects similar to thethird embodiment will also be achieved.

Seventh Embodiment

A seventh embodiment will be described with reference to FIG. 14.

A voltage detecting device 81 is provided by modifying the structure ofthe second switches of the voltage detecting device 61 of the sixthembodiment. In particular, the second switch SW2 x is commonly disposedbetween the first end of the first capacitor C1 x of the first-sidecircuit unit connected to the inverted input terminal of the operationamplifier 52 and the first end of the first capacitor C1 x of thesecond-side circuit unit connected to the non-inverted input terminal ofthe operation amplifier 52. Other structures of the voltage detectingdevice 81 are similar to the structures of the voltage detecting device71 shown in FIG. 10.

In the period 4 where the second switch SW2 x is in the on state, when avoltage of the connection node between the two first capacitors C1 x isreferred to as VY, the conservation of the electric charge between theperiod 3 and the period 4 is expressed by the following general formulas(19) and (20). A formula (21) is obtained by subtracting the formula(20) from the formula (19). That is, by adjusting the capacitance ratio,the differential output voltage VOP−VOM is the same as that expressed bythe formula (15) of the sixth embodiment.

C1(Vn−VCOM)+C2(VA−VCOM)=C1(VY−VX)+C2(VOP−VX)  (19)

C1(Vn−1−VCOM)+C2(VB−VCOM)=C1(VY−VX)+C2(VOM−VX)  (20)

VOP−VOM=C1/C2(Vn−Vn−1)+(VA−VB)  (21)

In the present embodiment, not only when the common mode noise isoverlapped on the assembled battery 1 at the time of charging the firstcapacitor C1 x, but also when the common mode noise is overlapped on theassembled battery 1 at the time of the redistribution of the electriccharge, the common mode noise can be removed from the differentialoutput voltage VOP−VOM of the operation amplifier 52 and from the inputside common voltage VX of he operation amplifier 52. In regard to theerror due to the field through and the effect of the offset voltage ΔVOSof the operation amplifier 52, the advantageous effects similar thesixth embodiment will also be achieved.

Eighth Embodiment

An eighth embodiment will be described with reference to FIGS. 15 and16.

A voltage detecting device 91 is provided by adding a voltage-dividingcircuit 92, a third capacitor C3, a seventh switch SW7 and an eighthswitch SW8 to the voltage detecting device 2 shown in FIG. 1, so as todetect a divided voltage VDIV of an entire voltage VBLK of the entireassembled battery 1.

A sixth switch SW6 and the voltage-dividing circuit 92 are connected inseries, between a high potential terminal TBH and a low potentialterminal TBO (ground). The voltage-dividing circuit 92 is provided by aseries circuit of a resistor R1 and a resistor R2 connected in series toeach other. A voltage dividing node of the resistor R1 and the resistorR2 is connected to a first end of the third capacitor C3. The seventhswitch SW7 is connected between the common line CL and a second end ofthe third capacitor C3. The second end of the third capacitor C3 can beapplied with the specified voltage VREF through the eighth switch SW8.The sixth switch SW6, the seventh switch SW7 and the eighth switch SW8are provided by MOS transistors. The sixth switch SW6, the seventhswitch SW7 and the eighth switch SW8 are controlled by the controlcircuit 6.

Next, an operation of the voltage detecting device 91 will be describedwith reference to FIG. 16. Hereinafter, an operation of the voltagedetecting device 91 different from the operation of the first embodimentwill be mainly described.

In the period 1, the control circuit 6 turns on the sixth switch SW6 andthe eighth switch SW8 in addition to the first switches SW1A to SW1D,the fourth switch SW4, and the fifth switches SW5A to SW5D, and turnsoff the seventh switch SW7 in addition to the second switches SW2A toSW2D and the third switches SW3A to SW3D. Thus, the first capacitors C1Ato C1D are charged, as well as the third capacitor C3 is charged at thedivided voltage VDIV (sampling).

In the period 2, the control circuit 6 turns off the fifth switches SW5Ato SW5D and the eighth switch SW8 simultaneously (at the same time), sothat the first capacitors C1A to C1D and the third capacitor C3 hold theelectric charge at the same time (holding). The period 1 and the period2 are not only the charging period and the holding period, but also aresetting period of the second capacitor C2 for detecting the dividedvoltage VDIV. In the period 3, the control circuit 6 turns off the sixthswitch SW6 and the fourth switch SW4 in preparation for theredistribution of the electric charge of the period 4.

In the period 4, the control circuit 6 turns on the seventh switch SW7,and detects the divided voltage VDIV of the assembled battery 1. In thiscase, the electric charge held in the third capacitor C3 in the period 2is redistributed with the second capacitor C2. The voltage VBLK of andthe divided voltage VDIV of the assembled battery 1 satisfy arelationship expressed by the following formula (22). Also, theconservation of the electric charge between the period 3 and the period4 is expressed by the following formula (23). In this case, the voltagedivision ratio R2/(R1+R2) may be set equal to a value obtained bydividing 1 by the total number of the battery cells (i.e., 1/total cellnumber).

VDIV=R2/(R1+R2)×VBLK  (22)

C3(VDIV−VREF)=C3(0−VREF)+C2(VOUT−VREF)  (23)

The following formula (24) is derived by solving the formula (22) andthe formula (23).

VOUT=(C1/C2)VDIV+VREF  (24)

In the period 5, the control circuit 6 turns off the seventh switch SW7and turns on the eighth switch SW8. If the sampling operation is startedin a state where the sixth switch SW6 is turned on, an electric currentflows in the voltage-dividing circuit 92, resulting in loss. Therefore,the sixth switch 6 is kept in the off state to be in the standbyoperation, until the period 1 begins next. From the period 5 to theperiod 16, the control circuit 6 detects the cell voltages VB4 to VB1 ina sequence order.

In the present embodiment, the management device of the assembledbattery 1 can perform a fault diagnosis of the voltage detecting device91 by comparing the addition of the cell voltages VBn of the batterycells Bn and the entire voltage VBLK of the entire assembled battery 1.For example, a differential voltage (absolute value) between the totaladdition voltage of the cell voltages Bn and the entire voltage VBLK ofthe assembled battery 1 is calculated. When the differential voltage islower than a predetermined threshold, it is determined that the voltagedetecting device 91 is normal. When the differential voltage is equal toor higher than the predetermined threshold, it is determined that thevoltage detecting device 91 has a fault.

The cell voltages Bn of all the battery cells Bn and the divided voltageVDIV of the assembled battery 1 are sampled at the same time. Therefore,even if a variation in battery voltage is large, the fault determinationcan be accurately performed. The fault determination may be performed bythe control circuit 6. Also in ninth to fourteenth embodiments whichwill be described later, the fault determination may be performed by thecontrol circuit 6. Since the fault determination is performed, thereliability of the cell voltages VBn detected by the voltage detectingdevice 91 improves.

Ninth Embodiment

A ninth embodiment will be described with reference to FIGS. 17 and 18.

As shown in FIG. 17, a voltage detecting device 101 has a structuresimilar to the voltage detecting device 91 shown in FIG. 15, but thefifth switches SW5A to SW5D and the eighth switch SW8 are deleted.

In the period 1, the control circuit 6 turns on the first switches SW1Ato SW1D, the third switches SW3A to SW3D, the fourth switch SW4, thesixth switch SW6 and the seventh switch SW7, and turns off the secondswitches SW2A to SW2D. Thus, the operation amplifier 4 operates in avoltage follower. The first capacitors C1A to C1D are charged, and thethird capacitor C3 is charged at the divided voltage VDIV (sampling).

In the period 2, the control circuit 6 turns on the third switches SW3Ato SW3D and the seventh switch SW7 simultaneously (at the same time), sothat the first capacitors C1A to C1D and the third capacitor C3 hold theelectric charge at the same time (holding). The period 1 and the period2 are not only the charging period and the holding period, but also theresetting period of the second capacitor C2 for detecting the dividedvoltage VDIV. In the period 3, the control circuit 6 turns off the sixthswitch SW6 and the fourth switch SW4 in preparation for theredistribution of the electric charge of the period 4.

In the period 4, the control circuit 6 turns on the seventh switch SW7,and detects the divided voltage VDIV of the assembled battery 1. In thiscase, the electric charge held in the third capacitor C3 in the period 2is redistributed with the second capacitor C2, and the operationamplifier 4 outputs the voltage VOUT expressed by the formula (24). Inperiod 5, the control circuit 6 turns off the seventh switch SW7 toshift to a standby operation for the divided voltage VDIV. From theperiod 5 to the period 16, the control circuit 6 detects the cellvoltages VB4 to VB1 in a sequence order.

In the present embodiment, the advantageous effects similar to thesecond and eighth embodiment will be achieved.

Tenth Embodiment

A tenth embodiment will be described with reference to FIGS. 19 and 20.

As shown in FIG. 19, a voltage detecting device 111 is provided bymodifying the structures of the second capacitor and the fourth switchin the voltage detecting device 101 shown in FIG. 17, so as to removethe effect of the offset voltage of the operation amplifier 4. Thesecond capacitor and the fourth switch have the structures similar tothe second capacitor and the fourth switch shown in FIG. 9.

As shown in FIG. 20, in the period 1, the control circuit 6 turns on thefourth-A switch SW4A and the fourth-C switch SW4C, and turns off thefourth-B switch SW4B. In the period 3, the control circuit 6 turns offthe fourth-A switch SW4A and the fourth-C switch SW4C. In the period 4,the control circuit 6 turns on the fourth-B switch SW4B.

In the present embodiment, the advantageous effects similar to the thirdand ninth embodiments will be achieved.

Eleventh Embodiment

An eleventh embodiment will be described with reference to FIG. 21.

As shown in FIG. 11, a voltage detecting device 121 is provided bymodifying the structure shown in FIG. 15 for detecting the dividedvoltage VDIV of the assembled battery 1 into a differential type andadding the modified structure to the voltage detecting device 51 shownin FIG. 11.

In the first-side circuit unit, which corresponds to the inverted inputterminal of the operation amplifier 52, the first end of the thirdcapacitor C3 is connected to the voltage-dividing node of thevoltage-dividing circuit 92. In the second-side circuit unit, whichcorresponds to the non-inverted input terminal of the operationamplifier 52, the first end of the third capacitor C3 is connected tothe terminal TBO (ground). The control circuit 6 performs a switchcontrol similar the eighth embodiment shown in FIG. 16.

In the present embodiment, the advantageous effects similar to thefourth and eighth embodiments will be achieved.

Twelfth Embodiment

A twelfth embodiment will be described with reference to FIG. 22.

As shown in FIG. 12, a voltage detecting device 131 is provided bymodifying the structure shown in FIG. 17 for detecting the dividedvoltage VDIV of the assembled battery 1 into a differential type andadding the modified structure to the voltage detecting device 61 shownin FIG. 12.

In the first-side circuit unit, which corresponds to the inverted inputterminal of the operation amplifier 52, the first end of the thirdcapacitor C3 is connected to the voltage-dividing node of thevoltage-dividing circuit 92. In the second-side circuit unit, whichcorresponds to the non-inverted input terminal of the operationamplifier 52, the first end of the third capacitor C3 is connected tothe terminal TBO (ground). The control circuit 6 performs a switchcontrol similar the ninth embodiment shown in FIG. 18.

In the present embodiment, the advantageous effects similar to the fifthand ninth embodiments will be achieved.

Thirteenth Embodiment

A thirteenth embodiment will be described with reference to FIG. 23.

As shown in FIG. 23, a voltage detecting device 141 is provided bymodifying the structure shown in FIG. 19 for detecting the dividedvoltage VDIV of the assembled battery 1 into a differential type andadding the modified structure to the voltage detecting device 71 shownin FIG. 13. The control circuit 6 performs a switch control similar tothe tenth embodiment shown in FIG. 20.

In the present embodiment, the advantageous effects similar to the sixthand tenth embodiments will be achieved.

Fourteenth Embodiment

A fourteenth embodiment will be described with reference to FIG. 24.

As shown in FIG. 24, a voltage detecting device 151 is provided bymodifying the structure shown in FIG. 19 for detecting the dividedvoltage VDIV of the assembled battery 1 into a differential type andadding the modified structure to the voltage detecting device 81 shownin FIG. 14. The control circuit 6 performs a switch control similar tothe tenth embodiment shown in FIG. 20.

In the present embodiment, the advantageous effects similar to theseventh and tenth embodiments will be achieved.

Other Embodiments

The exemplary embodiments of the present disclosure are describedhereinabove. However, the present disclosure may not be limited to theexemplary embodiments described hereinabove, but may be modified invarious other ways without departing from the gist of the presentdisclosure.

In each of the embodiments described above, the electric charge of thesecond capacitor C2 is reset by turning on the fourth switch SW4, thefourth-A switch SW4A, or the fourth-C switch SW4C in the period 1 wherethe first capacitors C1 x are simultaneously charged. Therefore, aresetting process of the electric charge of the second capacitor C2 canbe deleted for the battery cell B4 that is set to the target cell fordetecting the voltage firstly after the holding of the electric charge,or for the entire assembled battery 1. In place of the above operation,that is, in place of resetting the electric charge of the secondcapacitor C2 in the period 1, the resetting period similar to the period5, 8, 11, 14 may be provided between the period 1 and the period 2.

The specified voltage may be set to a voltage different from thereference voltage VREF as long as a differential voltage with thereference voltage VREF is equal to or lower than the withstand voltageof the switches SW3 x, SW5 x, SW7 and SW8.

In the first and fourth embodiments, it is not always necessary to turnoff the second switch SW2 x corresponding to the target cell and to turnon the first switch SW1 x and the fifth switch SW5 x corresponding tothe target cell, immediately after the period 4, period 7 and period 10.These switch operations may be performed at least before the beginningof the next period 1, which is the next simultaneous sampling period.This may be similarly adoptable to the eighth embodiment and to theeleventh embodiment.

In the second, third, fifth, sixth and seventh embodiments, it is notalways necessary to turn off the second switch SW2 x corresponding tothe target cell immediately after the period 4, the period 7 and theperiod 10. Further, it is not always necessary to immediately turn offthe third switch SW3 x, as long as the first switch SW1 x and the secondswitch SW2 x are turned off.

These switch operation may be adoptable to the ninth, tenth, twelfth,thirteenth and fourteenth embodiments.

After the simultaneous holding (sampling) of the electric charge in thefirst capacitors C1A to C1D, the detection of the cell voltage VBn usingthe electric charge held may be performed in arbitrary order. Likewise,after the simultaneous holding (sampling) of the electric charge in thefirst capacitors C1A to C1D and the third capacitor C3, the detection ofthe divided voltage VDIV and the cell voltage VBn using the electriccharge may be performed in arbitrary order.

Summarizing the embodiments, the voltage detecting device is configuredto detect the voltage of each of the plurality of unit batteries B1 toB4 of the assembled battery 1 connected in series. The voltage detectingdevice may include an operation amplifier having an inverted inputterminal and a non-inverted input terminal; a plurality of firstcapacitors being correspondingly provided for the plurality of unitbatteries; a plurality of first switches each being disposed between ahigh potential terminal of corresponding one of the unit batteries and afirst end of corresponding one of the first capacitors; a plurality ofsecond switches each being disposed between a low potential terminal ofcorresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors, the low potential terminalhaving a potential lower than that of the high potential terminal; aplurality of third switches each being disposed between the invertedinput terminal of the operation amplifier and a second end ofcorresponding one of the first capacitors; a second capacitor and afourth switch being disposed in parallel between the inverted inputterminal of the operation amplifier and an output terminal of theoperation amplifier; a plurality of fifth switches each being disposedbetween a voltage line and the second end of corresponding one of thefirst capacitors, the voltage line being applied with a specifiedvoltage; and a control unit controlling the first switches, the secondswitches, the third switches, the fourth switch and the fifth switchesto detect the voltage of each of the unit batteries. In this case, thecontrol unit may close the first switches and the fifth switches tocharge electric charge to the first capacitors and then simultaneouslyopen at least one of the first switches or the fifth switches to holdthe electric charge in the first capacitors. Thereafter, while selectingone of the unit batteries in a predetermined order as a target unitbattery for voltage detection, the control unit may temporarily closethe fourth switch to reset electric charge of the second capacitor, andclose one of the second switches corresponding to the target unitbattery and one of the third switches corresponding to the target unitbattery, in a state where one of the first switches corresponding to thetarget unit battery and one of the fifth switches corresponding to thetarget unit battery are opened, to detect the voltage of the target unitbattery.

In this case, the electric charge of the unit batteries is sampled atthe same time, and then the voltages of the unit batteries are detectedin a predetermined order using the electric charge sampled. Therefore,the time of measuring the internal resistance and the terminal opencircuit voltage of the unit batteries can be shortened, as compared witha conventional structure. Also a circuit for the operation amplifier andthe switches may be provided by a low withstand voltage transistor, anda layout area can be reduced.

The operation amplifier may be a single-end operation amplifier. In thiscase, the non-inverted input terminal of the operation amplifier may bebiased to a predetermined reference voltage, and the specified voltageof the voltage line may be specified so that a voltage differencebetween the reference voltage and the specified voltage is equal to orless than a withstand voltage of the fifth switch.

The voltage detecting device may detect a divided voltage of the entirevoltage of the assembled battery in addition to the voltage detection ofeach of the unit batteries. In this case, the voltage detecting devicemay further include: a sixth switch and a voltage-dividing circuit beingdisposed in series to each other, between a high potential terminal ofthe assembled battery and a low potential terminal of the assembledbattery, the low potential terminal of the assembled battery having apotential lower than that of the high potential terminal of theassembled battery; a third capacitor having a first end connected to avoltage-dividing node of the voltage-dividing circuit; a seventh switchbeing disposed between the inverted input terminal of the operationamplifier and a second end of the third capacitor; and an eighth switchdisposed between the voltage line applied with the specified voltage andthe second end of the third capacitor.

In this case, when the control unit closes the first switches and thefifth switches to charge the electric charge to the first capacitors,the control unit may also close the sixth switch and the eighth switchto charge electric charge to the third capacitor. Further, when thecontrol unit simultaneously opens the at least one of the first switchesor the fifth switches to hold the electric charge in the firstcapacitors, the control unit may also open the eighth switch to hold theelectric charge in the third capacitor. After the electric charge of thesecond capacitor is reset, the control unit may close the seventh switchin a state where the sixth switch and the eighth switch are opened, anddetect a divided voltage of an entire voltage of the assembled battery.

In this case, the voltage detecting device can sample the voltages ofthe unit batteries and the divided voltage of the assembled battery atthe same time, and then the divided voltage and the assembled batteryand the voltages of the unit batteries are detected in a predeterminedorder using the sampled electric charge. Therefore, diagnose of thevoltage detecting device can be accurately performed based on comparisonof the total voltage of the detected voltages of the unit batteries andthe voltage of the entire assembled battery.

The voltage detecting device may be configured as a full differentialstructure, and the operation amplifier may be a differential outputoperation amplifier, in place of the single-end operation amplifier. Thedifferential output operation amplifier may have a common voltage as areference voltage. In this case, the first switches, the secondswitches, the third switches, the fourth switch, the fifth switches, thefirst capacitors and the second capacitor may be included in a firstside circuit unit provided on a first side of the operation amplifiercorresponding to the inverted input terminal and a non-inverted outputterminal of the operation amplifier. Further, the voltage detectingdevice may further include a second side circuit unit provided on asecond side of the operation amplifier corresponding to the non-invertedinput terminal and an inverted output terminal of the operationamplifier. The second side circuit unit includes the first switches, thesecond switches, the third switches, the fourth switch and the fifthswitches, the first capacitors and the second capacitor. In the firstside circuit unit, the second capacitor and the fourth switch aredisposed in parallel between the inverted input terminal of theoperation amplifier and the non-inverted output terminal of theoperation amplifier. In the second side circuit unit, each of the firstswitches is disposed between the low potential terminal of correspondingone of the unit batteries and the first end of corresponding one of thefirst capacitors; each of the second switches is disposed between thehigh potential terminal of corresponding one of the unit batteries andthe first end of corresponding one of the first capacitors; each of thethird switches is disposed between the non-inverted input terminal ofthe operation amplifier and the second end of corresponding one of thefirst capacitors; the second capacitor and the fourth switch aredisposed in parallel between the non-inverted input terminal of theoperation amplifier and the inverted output terminal of the operationamplifier; and each of the fifth switches is disposed between thevoltage line applied with the specified voltage and the second end ofcorresponding one of the first capacitors.

In this case, even if common mode noise overlaps on the assembledbattery in the charging of the first capacitors where the first switchesand the fifth switches are closed or in the electric chargeredistribution where the second switches are closed, the common modenoise can be removed from the output voltage of the operation amplifier.Further, since the circuit has a symmetric structure, an error due tofield through, which occurs when the switches are operated, can becancelled. Therefore, the detection accuracy improves.

Also in this case, the full differential-type voltage detecting devicemay be configured to detect the divided voltage of the assembled batterytogether with the voltage detection of the unit batteries.

In the voltage detecting device, the fifth switches may be deleted.Namely, a voltage detecting device may include the operation amplifier,the plurality of first capacitors, the plurality of first switches, theplurality of second switches, the plurality of third switches, thesecond capacitor, the fourth switch, and the control unit. In this case,the control unit may close the first switches and the third switches tocharge electric charge to the first capacitors, in a state where thefourth switch is closed and the operation amplifier is operated in avoltage follower, and simultaneously open at least one of the firstswitches or the third switches to hold the electric charge in the firstcapacitors. Then, while selecting one of the unit batteries in apredetermined order as a target unit battery for voltage detection, thecontrol unit may temporarily close the fourth switch to reset electriccharge of the second capacitor, and close one of the second switchescorresponding to the target unit battery and one of the third switchescorresponding to the target unit battery, in a state where one of thefirst switches corresponding to the target unit battery is opened, todetect the voltage of the target unit battery. Also in this case, thesimilar advantageous effects described hereinabove will be achieved.Also, since the fifth switches are unnecessary, the layout area can bereduced.

Also in this voltage detecting device, the operation amplifier may be asingle-end operation amplifier. Alternatively, the voltage detectingdevice may be configured into a full-differential structure and theoperation amplifier may be a differential output operation amplifier.Further, the voltage detecting device may be configured to detect thedivided-voltage of the entire voltage of the assembled battery inaddition to the voltage detection of each of the unit batteries

The voltage detecting device may include an operation amplifier havingan inverted input terminal and a non-inverted input terminal; aplurality of first capacitors being correspondingly provided for theplurality of unit batteries; a plurality of first switches each beingdisposed between a high potential terminal of corresponding one of theunit batteries and a first end of corresponding one of the firstcapacitors; a plurality of second switches each being disposed between alow potential terminal of corresponding one of the unit batteries andthe first end of corresponding one of the first capacitors, the lowpotential terminal having a potential lower than that of the highpotential terminal; a plurality of third switches each being disposedbetween the inverted input terminal of the operation amplifier and asecond end of corresponding one of the first capacitors; a fourth switchbeing disposed between the inverted input terminal of the operationamplifier and an output terminal of the operation amplifier; a secondcapacitor and a ninth switch being disposed in series, between theinverted input terminal of the operation amplifier and the outputterminal of the operation amplifier; a tenth switch being disposedbetween a common connecting point of the second capacitor and the ninthswitch and a voltage line applied with a constant voltage; and a controlunit controlling the first switches, the second switches, the thirdswitches, the fourth switch, the ninth switch and the tenth switch todetect the voltage of each of the unit batteries. The control unitcloses the first switches and the third switches to charge electriccharge to the first capacitors, in a state where the fourth switch isclosed and the operation amplifier is operated in a voltage follower,and simultaneously opens at least one of the first switches or the thirdswitches to hold the electric charge in the first capacitors. Then,while selecting one of the unit batteries in a predetermined order as atarget unit battery for voltage detection, the control unit temporarilycloses the fourth switch and the tenth switch to reset electric chargeof the second capacitor; and closes the ninth switch, one of the secondswitches corresponding to the target unit battery, and one of the thirdswitches corresponding to the target unit battery, in a state where oneof the first switches corresponding to the target unit battery isopened, to detect the voltage of the target unit battery.

In this case, the advantageous effects described hereinabove will bealso achieved. Further, the offset voltage of the operation amplifiercan be removed from the detected voltage of the unit batteries.

Also in this voltage detecting device, the operation amplifier may be asingle-end operation amplifier. Alternatively, the voltage detectingdevice may be configured into a full differential structure, and theoperation amplifier may be a differential output operation amplifier. Inthis case, the voltage detecting device may have the first side circuitunit and the second side circuit unit. However, the first side circuitunit and the second side circuit unit may share the second switchesbetween them. Each of the second switches may be disposed between thefirst end of corresponding one of the first capacitors of the first sidecircuit unit and the first end of corresponding one of the firstcapacitors of the second side circuit unit.

In this case, the first end of the first capacitor may be separated fromthe assembled battery and becomes a floating condition, during theredistribution of the electric charge. Therefore, even if common modenoise overlaps on the assembled battery during the charging of the firstcapacitor by closing the first switch or during the redistribution ofthe electric charge by closing the second switch, the effect of thecommon mode noise can be removed from the common voltage of the inputterminal of the operation amplifier.

Also in this case, the voltage detecting device may be configured todetect the divided voltage of the assembled battery together with thevoltage detection of the unit batteries

In the voltage detecting device described in the above embodiments, thecontrol unit may omit resetting of the electric charge of the secondcapacitor for a first target unit battery that is selected first afterthe electric charge is simultaneously held in the first capacitors, oncondition that the fourth switch is closed in a period where theelectric charge is simultaneously charged in the first capacitors. Thecontrol unit may omit resetting of the electric charge of the secondcapacitor for a first target unit battery that is selected first afterthe electric charge is simultaneously held in the first capacitors andthe third capacitors, on condition that the fourth switch is closed in aperiod where the electric charge is simultaneously charged in the firstcapacitors and the third capacitors. The control unit may omit resettingof the electric charge of the second capacitor for a first target unitbattery that is selected first after the electric charge issimultaneously held in the first capacitors, on condition that thefourth switch and the tenth switch are closed in a period where theelectric charge is simultaneously charged in the first capacitors. Thecontrol unit may omit resetting of the electric charge of the secondcapacitor for a first target unit battery that is selected first afterthe electric charge is simultaneously held in the first capacitors andthe third capacitors, on condition that the fourth switch and the tenthswitch are closed in a period where the electric charge issimultaneously charged in the first capacitors and the third capacitors.In these cases, the time for the voltage detection can be shortened.

In the voltage detecting device having the sixth switch and thevoltage-dividing circuit, the control unit may compare a total voltageof the voltages detected for the plurality of unit batteries with anentire voltage of the assembled voltage obtained from the dividedvoltage detected, and may determine a malfunction of the voltagedetecting device. In this case, even if the fluctuation of the batteryvoltage is large, the malfunction can be accurately determined.

The above described structures may be combined in any ways. While onlythe selected exemplary embodiment and examples have been chosen toillustrate the present disclosure, it will be apparent to those skilledin the art from this disclosure that various changes and modificationscan be made therein without departing from the scope of the disclosureas defined in the appended claims. Furthermore, the foregoingdescription of the exemplary embodiment and examples according to thepresent disclosure is provided for illustration only, and not for thepurpose of limiting the disclosure as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A voltage detecting device for detecting avoltage of each of a plurality of unit batteries of an assembledbattery, the unit batteries being connected in series, the voltagedetecting device comprising: an operation amplifier having an invertedinput terminal and a non-inverted input terminal; a plurality of firstcapacitors being correspondingly provided for the plurality of unitbatteries; a plurality of first switches each being disposed between ahigh potential terminal of corresponding one of the unit batteries and afirst end of corresponding one of the first capacitors; a plurality ofsecond switches each being disposed between a low potential terminal ofcorresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors, the low potential terminalhaving a potential lower than that of the high potential terminal; aplurality of third switches each being disposed between the invertedinput terminal of the operation amplifier and a second end ofcorresponding one of the first capacitors; a second capacitor and afourth switch being disposed in parallel between the inverted inputterminal of the operation amplifier and an output terminal of theoperation amplifier; a plurality of fifth switches each being disposedbetween a voltage line and the second end of corresponding one of thefirst capacitors, the voltage line being applied with a specifiedvoltage; and a control unit controlling the first switches, the secondswitches, the third switches, the fourth switch and the fifth switchesto detect the voltage of each of the unit batteries, wherein the controlunit: closes the first switches and the fifth switches to chargeelectric charge to the first capacitors; simultaneously opens at leastone of the first switches or the fifth switches to hold the electriccharge in the first capacitors; temporarily closes the fourth switch toreset electric charge of the second capacitor, while selecting one ofthe unit batteries in a predetermined order as a target unit battery forvoltage detection; and closes one of the second switches correspondingto the target unit battery and one of the third switches correspondingto the target unit battery, in a state where one of the first switchescorresponding to the target unit battery and one of the fifth switchescorresponding to the target unit battery are opened, to detect thevoltage of the target unit battery.
 2. The voltage detecting deviceaccording to claim 1, wherein the operation amplifier is a single-endoperation amplifier, the non-inverted input terminal of the operationamplifier is biased to a predetermined reference voltage, and thespecified voltage of the voltage line is specified so that a voltagedifference between the reference voltage and the specified voltage isequal to or less than a withstand voltage of the fifth switch.
 3. Thevoltage detecting device according to claim 2, further comprising: asixth switch and a voltage-dividing circuit being disposed in series toeach other, between a high potential terminal of the assembled batteryand a low potential terminal of the assembled battery, the low potentialterminal of the assembled battery having a potential lower than that ofthe high potential terminal of the assembled battery; a third capacitorhaving a first end connected to a voltage-dividing node of thevoltage-dividing circuit; a seventh switch being disposed between theinverted input terminal of the operation amplifier and a second end ofthe third capacitor; and an eighth switch disposed between the voltageline applied with the specified voltage and the second end of the thirdcapacitor, wherein when the control unit closes the first switches andthe fifth switches to charge the electric charge to the firstcapacitors, the control unit also closes the sixth switch and the eighthswitch to charge electric charge to the third capacitor, when thecontrol unit simultaneously opens the at least one of the first switchesor the fifth switches to hold the electric charge in the firstcapacitors, the control unit also opens the eighth switch to hold theelectric charge in the third capacitor, and after the electric charge ofthe second capacitor is reset, the control unit closes the seventhswitch in a state where the sixth switch and the eighth switch areopened, and detects a divided voltage of an entire voltage of theassembled battery.
 4. The voltage detecting device according to claim 1,the voltage detecting device being configured into a full differentialstructure, wherein the operation amplifier is a differential outputoperation amplifier, the first switches, the second switches, the thirdswitches, the fourth switch, the fifth switches, the first capacitorsand the second capacitor are included in a first side circuit unitprovided on a first side of the operation amplifier corresponding to theinverted input terminal and a non-inverted output terminal of theoperation amplifier, the voltage detecting device further comprising asecond side circuit unit provided on a second side of the operationamplifier corresponding to the non-inverted input terminal and aninverted output terminal of the operation amplifier, the second sidecircuit unit including the first switches, the second switches, thethird switches, the fourth switch and the fifth switches, the firstcapacitors and the second capacitor, wherein in the first side circuitunit, the second capacitor and the fourth switch are disposed inparallel between the inverted input terminal of the operation amplifierand the non-inverted output terminal of the operation amplifier, in thesecond side circuit unit, each of the first switches is disposed betweenthe low potential terminal of corresponding one of the unit batteriesand the first end of corresponding one of the first capacitors, each ofthe second switches is disposed between the high potential terminal ofcorresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors, each of the third switches isdisposed between the non-inverted input terminal of the operationamplifier and the second end of corresponding one of the firstcapacitors, the second capacitor and the fourth switch are disposed inparallel between the non-inverted input terminal of the operationamplifier and the inverted output terminal of the operation amplifier,and each of the fifth switches is disposed between the voltage lineapplied with the specified voltage and the second end of correspondingone of the first capacitors.
 5. The voltage detecting device accordingto claim 4, further comprising: a sixth switch and a voltage-dividingcircuit being disposed in series to each other, between a high potentialterminal of the assembled battery and a low potential terminal of theassembled battery, the low potential terminal of the assembled batteryhaving a potential lower than that of the high potential terminal of theassembled battery; and a third capacitor, a seventh switch and an eighthswitch included in each of the first side circuit unit and the secondside circuit unit, wherein in the first side circuit unit, the thirdcapacitor has a first end connected to a voltage dividing node of thevoltage-dividing circuit, the seventh switch is disposed between theinverted input terminal of the operation amplifier and a second end ofthe third capacitor, and the eighth switch is disposed between thevoltage line applied with the specified voltage and the second end ofthe third capacitor, in the second side circuit unit, the thirdcapacitor has a first end connected to the low potential terminal of theassembled battery, the seventh switch is disposed between thenon-inverted input terminal of the operation amplifier and a second endof the third capacitor, and the eighth switch is disposed between thevoltage line applied with the specified voltage and the second end ofthe third capacitor, when the control unit closes the first switches andthe fifth switches to charge the electric charge to the firstcapacitors, the control unit also closes the sixth switches and theeighth switches to charge electric charge to the third capacitors, whenthe control unit simultaneously opens the at least one of the firstswitches or the fifth switches to hold the electric charge in the firstcapacitors, the control unit also opens the eighth switches to hold theelectric charge in the third capacitors, and after the electric chargeof the second capacitors is reset, the control unit closes the seventhswitches in a state where the sixth switches and the eighth switches areopened, and detects a divided voltage of an entire voltage of theassembled battery.
 6. A voltage detecting device for detecting a voltageof each of a plurality of unit batteries of an assembled battery, theunit batteries being connected in series, the voltage detecting devicecomprising: an operation amplifier having an inverted input terminal anda non-inverted input terminal; a plurality of first capacitors beingcorrespondingly provided for the plurality of unit batteries; aplurality of first switches each being disposed between a high potentialterminal of corresponding one of the unit batteries and a first end ofcorresponding one of the first capacitors; a plurality of secondswitches each being disposed between a low potential terminal ofcorresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors, the low potential terminalhaving a potential lower than that of the high potential terminal; aplurality of third switches each being disposed between the invertedinput terminal of the operation amplifier and a second end ofcorresponding one of the first capacitors; a second capacitor and afourth switch being disposed in parallel between the inverted inputterminal of the operation amplifier and an output terminal of theoperation amplifier; and a control unit controlling the first switches,the second switches, the third switches, and the fourth switch to detectthe voltage of each of the unit batteries, wherein the control unit:closes the first switches and the third switches to charge electriccharge to the first capacitors, in a state where the fourth switch isclosed and the operation amplifier is operated in a voltage follower;simultaneously opens at least one of the first switches or the thirdswitches to hold the electric charge in the first capacitors;temporarily closes the fourth switch to reset electric charge of thesecond capacitor, while selecting one of the unit batteries in apredetermined order as a target unit battery for voltage detection; andcloses one of the second switches corresponding to the target unitbattery and one of the third switches corresponding to the target unitbattery, in a state where one of the first switches corresponding to thetarget unit battery is opened, to detect the voltage of the target unitbattery.
 7. The voltage detecting device according to claim 6, whereinthe operation amplifier is a single-end operation amplifier, and thenon-inverted input terminal of the operation amplifier is biased to apredetermined reference voltage.
 8. The voltage detecting deviceaccording to claim 7, further comprising: a sixth switch and avoltage-dividing circuit being disposed in series to each other, betweena high potential terminal of the assembled battery and a low potentialterminal of the assembled battery, the low potential terminal of theassembled battery having a potential lower than that of the highpotential terminal of the assembled battery; a third capacitor having afirst end connected to a voltage-dividing node of the voltage-dividingcircuit; and a seventh switch being disposed between the inverted inputterminal of the operation amplifier and a second end of the thirdcapacitor, wherein when the control unit closes the first switches andthe third switches to charge electric charge to the first capacitors inthe state where the fourth switch is closed and the operation amplifieris operated in the voltage follower, the control unit also closes thesixth switch and the seventh switch to charge electric charge to thethird capacitor, when the control unit simultaneously opens the at leastone of the first switches or the third switches to hold the electriccharge in the first capacitors, the control unit also opens the seventhswitch to hold the electric charge in the third capacitor, and after theelectric charge of the second capacitor is reset, the control unitcloses the seventh switch in a state where the sixth switch is opened,and detects a divided voltage of an entire voltage of the assembledbattery.
 9. The voltage detecting device according to claim 6, thevoltage detecting device being configured into a full differentialstructure, wherein the operation amplifier is a differential outputoperation amplifier, the first switches, the second switches, the thirdswitches, the fourth switch, the first capacitors, and the secondcapacitor are included in a first side circuit unit provided on a firstside of the operation amplifier corresponding to the inverted inputterminal and a non-inverted output terminal of the operation amplifier,the voltage detecting device further comprising a second side circuitunit provided on a second side of the operation amplifier correspondingto the non-inverted input terminal and an inverted output terminal ofthe operation amplifier, the second side circuit unit including thefirst switches, the second switches, the third switches, the fourthswitch, the first capacitors and the second capacitor, wherein in thefirst side circuit unit, the second capacitor and the fourth switch aredisposed in parallel between the inverted input terminal of theoperation amplifier and the non-inverted output terminal of theoperation amplifier, in the second side circuit unit, each of the firstswitches is disposed between the low potential terminal of correspondingone of the unit batteries and the first end of corresponding one of thefirst capacitors, each of the second switches is disposed between thehigh potential terminal of corresponding one of the unit batteries andthe first end of corresponding one of the first capacitors, each of thethird switches is disposed between the non-inverted input terminal ofthe operation amplifier and the second end of corresponding one of thefirst capacitors, the second capacitor and the fourth switch aredisposed in parallel between the non-inverted input terminal of theoperation amplifier and the inverted output terminal of the operationamplifier.
 10. The voltage detecting device according to claim 9,further comprising: a sixth switch and a voltage-dividing circuit beingdisposed in series to each other, between a high potential terminal ofthe assembled battery and a low potential terminal of the assembledbattery, the low potential terminal of the assembled battery having apotential lower than that of the high potential terminal of theassembled battery; and a third capacitor and a seventh switch beingincluded in each of the first side circuit unit and the second sidecircuit unit, wherein in the first side circuit unit, the thirdcapacitor has a first end connected to a voltage-dividing node of thevoltage-dividing circuit, and the seventh switch is disposed between theinverted input terminal of the operation amplifier and a second end ofthe third capacitor, in the second side circuit unit, the thirdcapacitor has a first end connected to the low potential terminal of theassembled battery, and the seventh switch is disposed between thenon-inverted input terminal of the operation amplifier and a second endof the third capacitor, when the control unit closes the first switchesand the third switches to charge electric charge to the first capacitorsin the state where the fourth switches are closed and the operationamplifier is operated in the voltage follower, the control unit alsocloses the sixth switch and the seventh switches to charge electriccharge to the third capacitors, when the control unit simultaneouslyopens at least one of the first switches or the third switches to holdthe electric charge in the first capacitors, the control unit also opensthe seventh switches to hold the electric charge in the thirdcapacitors, and after the electric charge of the second capacitors isreset, the control unit closes the seventh switches in a state where thesixth switch is opened, and detects a divided voltage of an entirevoltage of the assembled battery.
 11. A voltage detecting device fordetecting a voltage of each of a plurality of unit batteries of anassembled battery, the unit batteries being connected in series, thevoltage detecting device comprising: an operation amplifier having aninverted input terminal and a non-inverted input terminal; a pluralityof first capacitors being correspondingly provided for the plurality ofunit batteries; a plurality of first switches each being disposedbetween a high potential terminal of corresponding one of the unitbatteries and a first end of corresponding one of the first capacitors;a plurality of second switches each being disposed between a lowpotential terminal of corresponding one of the unit batteries and thefirst end of corresponding one of the first capacitors, the lowpotential terminal having a potential lower than that of the highpotential terminal; a plurality of third switches each being disposedbetween the inverted input terminal of the operation amplifier and asecond end of corresponding one of the first capacitors; a fourth switchbeing disposed between the inverted input terminal of the operationamplifier and an output terminal of the operation amplifier; a secondcapacitor and a ninth switch being disposed in series, between theinverted input terminal of the operation amplifier and the outputterminal of the operation amplifier; a tenth switch being disposedbetween a common connecting point of the second capacitor and the ninthswitch and a voltage line applied with a constant voltage; and a controlunit controlling the first switches, the second switches, the thirdswitches, the fourth switch, the ninth switch and the tenth switch todetect the voltage of each of the unit batteries, wherein the controlunit: closes the first switches and the third switches to chargeelectric charge to the first capacitors, in a state where the fourthswitch is closed and the operation amplifier is operated in a voltagefollower; simultaneously opens at least one of the first switches or thethird switches to hold the electric charge in the first capacitors;temporarily closes the fourth switch and the tenth switch to resetelectric charge of the second capacitor, while selecting one of the unitbatteries in a predetermined order as a target unit battery for voltagedetection; and closes the ninth switch, one of the second switchescorresponding to the target unit battery, and one of the third switchescorresponding to the target unit battery, in a state where one of thefirst switches corresponding to the target unit battery is opened, todetect the voltage of the target unit battery.
 12. The voltage detectingdevice according to claim 11, wherein the operation amplifier is asingle-end operation amplifier, and the non-inverted input terminal ofthe operation amplifier is biased to a predetermined reference voltage.13. The voltage detecting device according to claim 12, furthercomprising: a sixth switch and a voltage-dividing circuit being disposedin series to each other, between a high potential terminal of theassembled battery and a low potential terminal of the assembled battery,the low potential terminal of the assembled battery having a potentiallower than that of the high potential terminal of the assembled battery;a third capacitor having a first end connected to a voltage-dividingnode of the voltage-dividing circuit; and a seventh switch beingdisposed between the inverted input terminal of the operation amplifierand a second end of the third capacitor, wherein when the control unitcloses the first switches and the third switches to charge the electriccharge to the first capacitors in the state where the fourth switch isclosed and the operation amplifier is operated in the voltage follower,the control unit also closes the sixth switch and the seventh switch tocharge electric charge to the third capacitor, when the control unitsimultaneously opens the at least one of the first switches or the thirdswitches to hold the electric charge in the first capacitors, thecontrol unit also opens the seventh switch to hold the electric chargein the third capacitor, and after the electric charge of the secondcapacitor is reset in a state where the fourth switch and the tenthswitch are temporarily closed, the control unit closes the seventhswitch in a state where the ninth switch is closed and the sixth switchis opened, and detects a divided voltage of an entire voltage of theassembled battery.
 14. The voltage detecting device according to claim11, the voltage detecting device being configured into a fulldifferential structure, wherein the operation amplifier is adifferential output operation amplifier, the first switches, the secondswitches, the third switches, the fourth switch, the ninth switch, thetenth switch, the first capacitors, and the second capacitor areincluded in a first side circuit unit provided on a first side of theoperation amplifier corresponding to the inverted input terminal and anon-inverted output terminal of the operation amplifier, the voltagedetecting device further comprising a second side circuit unit providedon a second side of the operation amplifier corresponding to thenon-inverted input terminal and an inverted output terminal of theoperation amplifier, the second side circuit unit including the firstswitches, the second switches, the third switches, the fourth switch,the ninth switch, the tenth switch, the first capacitors and the secondcapacitor, wherein in the first side circuit unit, the fourth switch isdisposed between the inverted input terminal of the operation amplifierand the non-inverted output terminal of the operation amplifier, thesecond capacitor and the ninth switch are disposed in series between theinverted input terminal of the operation amplifier and the non-invertedoutput terminal of the operation amplifier, in the second side circuitunit, each of the first switches is disposed between the low potentialterminal of corresponding one of the unit batteries and the first end ofcorresponding one of the first capacitors, each of the second switchesis disposed between the high potential terminal of corresponding one ofthe unit batteries and the first end of corresponding one of the firstcapacitors, each of the third switches is disposed between thenon-inverted input terminal of the operation amplifier and the secondend of corresponding one of the first capacitor, the fourth switch isdisposed between the non-inverted input terminal of the operationamplifier and the inverted output terminal of the operation amplifier,the second capacitor and the ninth switch are disposed in series betweenthe non-inverted input terminal of the operation amplifier and theinverted output terminal of the operation amplifier, and the tenthswitch is disposed between the common connecting point of the secondcapacitor and the ninth switch and the voltage line applied with theconstant voltage.
 15. The voltage detecting device according to claim11, the voltage detecting device being configured into a fulldifferential structure, wherein the operation amplifier is adifferential output operation amplifier, the first switches, the secondswitches, the third switches, the fourth switch, the ninth switch, thetenth switch, the first capacitors, and the second capacitor areincluded in a first side circuit unit on a first side of the operationamplifier corresponding to the inverted input terminal and anon-inverted output terminal of the operation amplifier, the voltagedetecting device further comprising a second side circuit unit providedon a second side of the operation amplifier corresponding to thenon-inverted input terminal and an inverted output terminal of theoperation amplifier, the second side circuit unit including the firstswitches, the third switches, the fourth switch, the ninth switch, thetenth switch, the first capacitors and the second capacitor, wherein inthe first side circuit unit, the fourth switch is disposed between theinverted input terminal of the operation amplifier and the non-invertedoutput terminal of the operation amplifier, the second capacitor and theninth switch are disposed in series between the inverted input terminalof the operation amplifier and the non-inverted output terminal of theoperation amplifier, in the second side circuit unit, each of the firstswitches is disposed between the low potential terminal of correspondingone of the unit batteries and the first end of corresponding one of thefirst capacitors, each of the third switches is disposed between thenon-inverted input terminal of the operation amplifier and the secondend of corresponding one of the first capacitors, the fourth switch isdisposed between the non-inverted input terminal of the operationamplifier and the inverted output terminal of the operation amplifier,the second capacitor and the ninth switch are disposed in series betweenthe non-inverted input terminal of the operation amplifier and theinverted output terminal of the operation amplifier, and the tenthswitch is disposed between the common connecting point of the secondcapacitor and the ninth switch and the voltage line applied with theconstant voltage, and the first side circuit unit and the second sidecircuit unit share the second switches, and each of the second switchesis disposed between the first end of corresponding one of the firstcapacitors of the first side circuit unit and the first end ofcorresponding one of the first capacitors of the second side circuitunit.
 16. The voltage detecting device according to claim 15, furthercomprising: a sixth switch and a voltage-dividing circuit being disposedin series to each other, between a high potential terminal of theassembled battery and a low potential terminal of the assembled battery,the low potential terminal of the assembled battery having a potentiallower than that of the high potential terminal of the assembled battery;and a third capacitor and a seventh switch being included in each of thefirst side circuit unit and the second side circuit unit, wherein in thefirst side circuit unit, the third capacitor has a first end connectedto a voltage-dividing node of the voltage-dividing circuit, and theseventh switch is disposed between the inverted input terminal of theoperation amplifier and a second end of the third capacitor, in thesecond side circuit unit, the third capacitor has a first end connectedto the low potential terminal of the assembled battery, and the seventhswitch is disposed between the non-inverted input terminal of theoperation amplifier and a second end of the third capacitor, when thecontrol unit closes the first switches and the third switches to chargeelectric charge to the first capacitors in the state where the fourthswitches are closed and the operation amplifier is operated in thevoltage follower, the control unit also closes the sixth switch and theseventh switches to charge electric charge to the third capacitors, whenthe control unit simultaneously opens at least one of the first switchesor the third switches to hold the electric charge in the firstcapacitors, the control unit also opens the seventh switches to hold theelectric charge in the third capacitors, and after the electric chargeof the second capacitors is reset in the state where the fourth switchesand the tenth switches are temporarily closed, the control unit closesthe seventh switches in a state where the ninth switches are closed andthe sixth switch is opened, and detects a divided voltage of an entirevoltage of the assembled battery.
 17. The voltage detecting deviceaccording to claim 14, further comprising: a sixth switch and avoltage-dividing circuit being disposed in series to each other, betweena high potential terminal of the assembled battery and a low potentialterminal of the assembled battery, the low potential terminal of theassembled battery having a potential lower than that of the highpotential terminal of the assembled battery; and a third capacitor and aseventh switch being included in each of the first side circuit unit andthe second side circuit unit, wherein in the first side circuit unit,the third capacitor has a first end connected to a voltage-dividing nodeof the voltage-dividing circuit, and the seventh switch is disposedbetween the inverted input terminal of the operation amplifier and asecond end of the third capacitor, in the second side circuit unit, thethird capacitor has a first end connected to the low potential terminalof the assembled battery, and the seventh switch is disposed between thenon-inverted input terminal of the operation amplifier and a second endof the third capacitor, when the control unit closes the first switchesand the third switches to charge electric charge to the first capacitorsin the state where the fourth switches are closed and the operationamplifier is operated in the voltage follower, the control unit alsocloses the sixth switch and the seventh switches to charge electriccharge to the third capacitors, when the control unit simultaneouslyopens at least one of the first switches or the third switches to holdthe electric charge in the first capacitors, the control unit also opensthe seventh switches to hold the electric charge in the thirdcapacitors, and after the electric charge of the second capacitors isreset in the state where the fourth switches and the tenth switches aretemporarily closed, the control unit closes the seventh switches in astate where the ninth switches are closed and the sixth switch isopened, and detects a divided voltage of an entire voltage of theassembled battery.
 18. The voltage detecting device according to claim1, wherein the control unit omits resetting of the electric charge ofthe second capacitor for a first target unit battery that is selectedfirst after the electric charge is simultaneously held in the firstcapacitors, on condition that the fourth switch is closed in a periodwhere the electric charge is simultaneously charged in the firstcapacitors.
 19. The voltage detecting device according to claim 3,wherein the control unit omits resetting of the electric charge of thesecond capacitor for a first target unit battery that is selected firstafter the electric charge is simultaneously held in the first capacitorsand the third capacitors, on condition that the fourth switch is closedin a period where the electric charge is simultaneously charged in thefirst capacitors and the third capacitors.
 20. The voltage detectingdevice according to claim 11, wherein the control unit omits resettingof the electric charge of the second capacitor for a first target unitbattery that is selected first after the electric charge issimultaneously held in the first capacitors, on condition that thefourth switch and the tenth switch are closed in a period where theelectric charge is simultaneously charged in the first capacitors. 21.The voltage detecting device according to claim 13, wherein the controlunit omits resetting of the electric charge of the second capacitor fora first target unit battery that is selected first after the electriccharge is simultaneously held in the first capacitors and the thirdcapacitors, on condition that the fourth switch and the tenth switch areclosed in a period where the electric charge is simultaneously chargedin the first capacitors and the third capacitors.
 22. The voltagedetecting device according to claim 2, wherein the specified voltage isset equal to the reference voltage.
 23. The voltage detecting deviceaccording to claim 3, wherein the control unit compares a total voltageof the voltages detected for the plurality of unit batteries with anentire voltage of the assembled voltage obtained from the dividedvoltage detected, and determines a malfunction of the voltage detectingdevice.